What are the uses of a laser pointer in astronomy?

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Laser pointers are used by astronomers to point to notable locations in the sky. They are popular tools for public stargazing with groups because they can easily direct the attention of the whole group to a particular constellation or celestial object. Laser pointers are also used as finders, tools that locate celestial objects and help an astronomer point the telescope toward the correct location for closer observation.

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The main kind of laser pointer used by astronomers both as a public stargazing tool and as a finder is the green laser. They are popular because, although they are normally inexpensive, they are capable of putting out a highly intense light beam that can be visible for hundreds of yards. This allows them to point very accurately at objects high above the ground. They are preferred to the even more common and less expensive red laser pointer because of a quirk of human anatomy. The human eye is particularly sensitive to green light, so green lasers are perceived as brighter than red lasers regardless of power setting.

Green laser pointers of the kind used by astronomers typically output 5 milliwatts or less of power. However, because laser light is highly concentrated into narrow beams, that amount of power is hazardous to the human eye if viewed directly. The beams themselves are not dangerous when viewed from the side, as they are when finding or pointing. However, when viewed head-on, they can cause temporary blindness, even at a great distance. The danger of strong laser light being pointed directly into pilots' eyes has led to numerous restrictions and guidelines on the use of these astronomical tools in many countries, including the United States, Canada and Australia.

Radio telescopes are important in astronomy because optical telescopes can only observe objects that emit or reflect light. As light comprises only a narrow range of the electromagnetic spectrum, radio telescopes have played a vital role in obtaining knowledge of the universe.

According to NASA, modern astronomers’ tools include advanced telescopes capable of studying light reflected from the sun, moon, planets, comets and stars. Radio telescopes are utilized in the study of radio waves, while space-borne gamma ray telescopes aid in the study of gamma rays.